Intro to Bacteria

Question 1

Structure of a bacterium

Answer 1

• Capsule
• Cell wall
• Plasma membrane
• Cytoplasms, ribosomes
• Single chromosome, no nucleus
• Flagellum
• Fimbriae - attachment

Question 2

Describe Gram positive cell wall

Answer 2

• Plasma membrane
• Periplasmic space
• Peptidoglycan

Question 3

Describe Gram negative cell wall

Answer 3

• Plasma membrane
• Periplasmic space
• Petidoglycan
• Another Peri. space
• Lipopolysaccharide nd protein outer membrane

Question 4

Difference between cell wall of gram pos. and neg.

Answer 4

Negative has enter Periplasmic space and outer membrane of lipopolysaccharide

-Pos. has thick peptidoglycan wall with techoic acid and neg. has thin

Question 5

What is the gram stain appearance of Gram positive?

Answer 5

Purple due to thick peptidoglycan wall

Question 6

What is the gram stain appearance of Gram negative?

Answer 6

Pink

Question 7

What is the shape of cocci?

Answer 7

Spepherical

Question 8

What is the shape of bacilli?

Answer 8

Rod shaped

Question 9

What do penicillin binding proteins do and name examples

Answer 9

Cross link peptidoglycan chains to form rigid cell walls

• Transpeptidases
• Carboxypeptidases
• Endopeptidases

Question 10

What is peptidoglycan?

Answer 10

Strong carbohydrate polymers cross linked with 3/5 amino acids

Question 11

Function of the capsule

Answer 11

Helps bacteria to survive in host system and prevents it being phagocytosed

Question 12

Describe the different types of Flagellum

Answer 12

• Montrichous - 1
• Lophotrichous - all at one point
• Amphitichous - both sides
• Peritrichous - all over

Question 13

Give examples of bacteria with flagellum

Answer 13

Eacherichia coli and salmonella enterica

Question 14

Function of fimbriae

Answer 14

Allow adhesion and cause infection

Question 15

Use of spores by bacterium

Answer 15

Ensures survival of bacterium during environmental stress

-Resistant to UV, gamma rays, desiccation, temp, starvation and chemical disinfectants

Question 16

Function of Periplasmic space

Answer 16

Contains enzymes important for digestion of materials, transporting material and detecting chemical gradients in environment

Question 17

What are plasmids?

Answer 17

• Small, circular, double stranded DNA

- Can replicate independently

Question 18

Bacterial conjugation steps

Answer 18

1. Donor cell (F+) produces pilus
2. Pilus attaches to recipient cell (F-)
3. Single strand of DNA from plasmid transferred to F-
4. Both cells synthesise complementary strand

Question 19

How to bacterium replicate?

Answer 19

Binary fission (asexually)

Question 20

How is variation introduced?

Answer 20

Spontaneous mutation (random) and transfer of DNA - dead cells present containing DNA and if it’s advantageous then it is taken up

Question 21

Describe process of binary fission

Answer 21

1. Cell replicates DNA
2. Cell elongates, separating DNA molecules
3. Division of bacterium - cytokinesis
4. Two new daughter cells (genetically identical)

Question 22

What is a bacteriophage?

Answer 22

A virus which attacks bacteria and lyses them

Question 23

Describe detection and culture of bacteria

Answer 23

• Individual bacteria can only be seen with microscope and gram staining
• Colonies of individual bacteria cultured on solid medium (agar and then can be seen by eye

Question 24

Bacterial nomenclature

Answer 24

• First part (i.e. staphylococcus) is genus

- Second part (i.e. aureus) is the species

Question 25

What technique is used to identify strained of a species?

Answer 25

DNA typing

-Strains of species have similar characteristics